This invention is generally directed to photoconductive imaging members with organic polymers as charge transport components. More specifically, the present invention is directed to layered imaging members with organic charge transport components selected from diaryl biarylylamine-based charge transport polymers. The aforementioned charge transport polymers possess a number of advantages including excellent charge transporting characteristics; they are environmentally safe, non-hazardous and non-toxic; and their structural simplicities render their synthesis easily executable by economic processes. In addition, the charge transport polymers of the present invention can be utilized as a single-component transport layer, that is wherein a binder resin is not used in the transport layer of layered imaging devices. Single-component transport layers provide, for example, long-term structural stability since they are devoid of the problem of small molecule crystallization commonly associated with charge transport molecules-in-binder transport layers. In addition, the charge transport polymers illustrated herein enable photoconductive imaging members that can be selected for electrophotographic imaging and printing processes for an extended number of imaging cycles, while avoiding or minimizing charge transport molecule crystallization. The imaging members of the present invention are especially suitable for imaging and printing apparatuses wherein liquid developers are selected, primarily since a single-component transport layer can be utilized, that is a resin binder is not needed in this embodiment, and the polymer, or polymers illustrated herein are selected, thereby eliminating the problem of charge transport molecule leaching and bleeding when the imaging members are in contact with liquid developers. Furthermore, the charge transport polymers of the present invention possess acceptable solubility in common organic solvents such as halogenated, especially chlorinated hydrocarbons, tetrahydrofuran, toluene, xylene, and the like, thus enabling improved coatability thereof by various processes such as spray, dip, and draw-down coating techniques. In one embodiment of the present invention, the imaging member is comprised of a supporting substrate, a photogenerating layer, and in contact therewith a charge transport layer comprised of diaryl biarylylamine-based charge transport polymers optionally, but not preferably, dispersed in inactive resinous binders, such as the optional binders selected for the photogenerating layer including polycarbonates. The charge transport layer can be located as the top layer of the imaging member, or alternatively it may be situated between the supporting substrate and the photogenerating layer.
The formation and development of electrostatic latent images on the imaging surfaces of photoconductive materials by electrostatic means is well known. Numerous different photoconductive members for use in xerography are known such as selenium, alloys of selenium, layered imaging members comprised of aryl amine charge transport layers, reference U.S. Pat. No. 4,265,990, and imaging members with charge transport layers comprised of polysilylenes, reference U.S. Pat. No. 4,618,551. The disclosures of the aforementioned patents are totally incorporated herein by reference. However, the layered imaging members with transport layers incorporating the diaryl biarylylamine-based polymers of the present invention are, for example, economically more attractive in most instances than, for example, the members of the '790 and '551 patents in respect of material and fabrication costs, and possess the other advantages illustrated herein. Further, the diaryl biarylylamine-based charge transport polymers of the present invention can be synthesized from readily available inexpensive starting materials via cost-effective synthetic processes. Also, in regard to photochemical stability, the charge transport polymers of the present invention are superior to, for example, polysilylenes, and the aforementioned transport polymers do not photodegrade when exposed to ultraviolet radiations.
There are also known photoreceptor materials comprised of inorganic or organic materials wherein the charge carrier generation and charge carrier transport functions are accomplished by discrete contiguous layers. Additionally, photoreceptor materials are disclosed in the prior art which include an overcoating layer of an electrically insulating polymeric material and in conjunction with this overcoated type photoreceptor there have been proposed a number of imaging methods.
Specifically, layered photoresponsive devices including those comprised of photogenerating layers and transport layers are disclosed as indicated herein in U.S. Pat. No. 4,265,990, and overcoated photoresponsive materials containing a hole injecting layer overcoated with a transport layer, followed by an overcoating of a photogenerating layer and a top coating of an insulating organic resin, reference U.S. Pat. No. 4,251,612. Examples of generating layers disclosed in these patents include trigonal selenium and vanadyl phthalocyanine, while examples of the charge transport layer that may be employed are comprised of the aryldiamines as mentioned therein. The '990 patent is of particular interest in that it discloses layered photoresponsive imaging members similar to those illustrated in the present application with the exception that the charge transporting component of the members of the present invention are comprised of charge transport polymers of the formulas illustrated herein. These members can be utilized in an electrophotographic method by, for example, initially charging the member with an electrostatic charge and imagewise exposing to form an electrostatic latent image which can be subsequently developed to form a visible image. Other representative patents disclosing layered photoresponsive devices include U.S. Pat. Nos. 4,115,116; 4,047,949 and 4,081,274.
As a result of a patentability search there was located (1) U.S. Pat. No. 4,025,341 which discloses imaging members with photoconductive polymers comprised of the condensation products of a tertiary amine having at least two phenyl groups, and a carbonyl-containing compound of the formula as illustrated in column 3, with examples of condensation polymers being provided in column 4, reference Formula II, noting especially the polymers when R.sub.5, R.sub.9, and R.sub.10 are each aryl(phenyl), however, it is believed that the polymers of the present invention are substantially different from those described in the '341 patent in that the invention polymers are polar charge transport polymers selected from, for example, the group consisting of polyesters, polycarbonates, polyurethanes and their copolymeric derivatives, while in contrast the polymers of U.S. Pat. No. 4,025,341 are nonpolar polymers whose backbones do not contain any carbonyl functions (C.dbd.O bond). Furthermore, the polymers of the present invention are formed from covalently linking suitable charge transport monomers via the C--O bonds rather than the C--C bonds as in the polymers of the '341 patent; (2) U.S. Pat. No. 4,725,518 which discloses imaging members wherein the charge transport layer is comprised of an aromatic amine compound and a protonic or Lewis acid; and (3) U.S. Pat. Nos. 3,567,450; 3,658,520; 4,025,341; 4,540,651; 4,606,988 and 4,769,302.
There is also disclosed in Belgium Patent No. 763,540 an electrophotographic member having at least two electrically operative layers, the first layer comprising a photoconductive layer which is capable of photogenerating charge carriers, and injecting the photogenerated holes into an active layer containing a transport organic material which is substantially nonabsorbing in the spectral region of intended use, but which is active and that allows injection of photogenerating holes from the photoconductive layer and allows these holes to be transported through the active layer. The active polymers may be mixed with inactive polymers or non-polymeric materials. Also, there is disclosed in U.S. Pat. Nos. 4,232,102 and 4,233,383, the disclosures of which are totally incorporated herein by reference, the selection of sodium carbonate doped and barium carbonate doped photoresponsive imaging members containing trigonal selenium.
U.S. Pat. No. 4,869,988, and copending patent application U.S. Ser. No. 274,160, entitled, respectively, PHOTOCONDUCTIVE IMAGING MEMBERS WITH N,N-BIS(BIARYLYL)ANILINE, OR TRIS(BIARYLYL)AMINE CHARGE TRANSPORTING COMPONENTS, and PHOTOCONDUCTIVE IMAGING MEMBERS WITH BIARYLYL DIARYLAMINE CHARGE TRANSPORTING COMPONENTS, the disclosures of which are totally incorporated herein by reference, there are described layered photoconductive imaging members with transport layers incorporating biarylyl diarylamines, N,N-bis(biarylyl)anilines, and tris(biarylyl)amines as charge transport compounds. More specifically, in this application and patent there are disclosed improved layered photoconductive imaging members comprised of a supporting substrate, a photogenerating layer, optionally dispersed in an inactive resinous binder, and in contact therewith a charge transport layer comprised of the above-mentioned charge transport compounds, or mixtures thereof dispersed in resinous binders. Examples of specific charge transporting components disclosed in the U.S. Pat. No. 4,869,988 include N,N-bis(4-biphenylyl)-3,5-dimethoxyaniline (Ia); N,N-bis(4-biphenylyl)-3,5-dimethylaniline (Ib); N,N-bis(4-methyl-4'-biphenylyl)-3-methoxyaniline (Ic); N,N-bis(4-methyl-4'-biphenylyl)-3-chloroaniline (Id); N,N-bis(4-methyl-4'-biphenylyl)-4-ethylaniline (Ie); N,N-bis(4-chloro-4'-biphenylyl)-3-methylaniline (If); N,N-bis(4-bromo-4'-biphenylyl)-3,5-dimethoxyaniline (Ig); 4-biphenylyl bis(4-ethoxycarbonyl-4'-biphenylyl)amine (IIa); 4-biphenylyl bis(4-acetoxymethyl-4'-biphenylyl)amine (IIb); 3-biphenylyl bis(4-methyl-4'-biphenylyl)amine (IIc); 4-ethoxycarbonyl-4'-biphenylyl bis(4-methyl-4'-biphenylyl)amine (IId); and the like.
Examples of specific charge transporting compounds disclosed in copending application U.S. Ser. No. 274,160 include bis(p-tolyl)-4-biphenylylamine (IIa); bis(p-chlorophenyl)-4-biphenylylamine (IIb); N-phenyl-N-(4-biphenylyl)-p-toluidine (IIc); N-(4-biphenylyl)-N-(p-chlorophenyl)-p-toluidine (IId); N-phenyl-N-(4-biphenylyl)-p-anisidine (IIe); bis(m-anisyl)-4-biphenylylamine (IIIa); bis(m-tolyl)-4-biphenylylamine (IIIb); bis(m-chlorophenyl)-4-biphenylylamine (IIIc); N-phenyl-N-(4-biphenylyl)-m-toluidine (IIId); N-phenyl-N-(4-bromo-4'-biphenylyl)-m-toluidine (IVa); diphenyl-4-methyl-4'-biphenylylamine (IVb); N-phenyl-N-(4-ethoxycarbonyl-4'-biphenylyl)-m-toluidine (IVc); N-phenyl-N-(4-methoxy-4'-biphenylyl)-m-toluidine (IVd); N-(m-anisyl)-N-(4-biphenylyl)-p-toluidine (IVe); bis(m-anisyl)-3-biphenylylamine (Va); N-phenyl-N-(4-methyl-3'-biphenylyl)-p-toluidine (Vb); N-phenyl-N-(4-methyl-3'-biphenylyl)-m-anisidine (Vc); bis(m-anisyl)-3-biphenylylamine (Vd); bis(p-tolyl)-4-methyl-3'-biphenylylamine (Ve); N-p-tolyl-N-(4-methoxy-3'-biphenylyl)-m-chloroaniline (Vf); and the like.
The following patent applications and U.S. patents are mentioned: (1) U.S. Pat. No. 4,818,650 describes layered imaging members with novel polymeric, hydroxy and alkoxy aryl amines, wherein m is a number of between about 4 and 1,000, reference for example claims 1 and 2; (2) U.S. Ser. No. 061,247 now abandoned and U.S. Pat. No. 4,871,634 illustrate imaging members with novel dihydroxy terminated aryl amine small molecules, reference claims 1 and 2, for example; (3) U.S. Pat. No. 4,806,444, the disclosure of which is totally incorporated herein by reference, describes layered imaging members with novel polycarbonate polymeric aryl amines, reference claims 1 and 2, for example; (4) U.S. Pat. No. 4,806,443, the disclosure of which is totally incorporated herein by reference, illustrates novel polycarbonate polymeric amines useful in layered imaging members, reference claims 1 and 2, for example; and (5) U.S. Pat. No. 4,801,517, the disclosure of which is totally incorporated herein by reference, which discloses imaging members with novel polycarbonate aryl amines, reference claims 1 and 2, for example.
While imaging members with various charge transporting substances, including the aryl amines of the above mentioned U.S. patents are suitable for their intended purposes, there continues to be a need for improved members, particularly layered members, which are comprised of single-component transport layers of charge transport polymers, thereby ensuring the long-term stability of the members. Another need resides in the provision of layered imaging members that are compatible with liquid developer compositions. Further, there continues to be a need for layered imaging members wherein the layers are sufficiently adhered to one another to allow the continuous use of such members in repetitive imaging systems. Also, there continues to be a need for improved layered imaging members whose transport layers are devoid of the problems of transport molecule crystallization. Furthermore, there continues to be a need for charge transporting copolymers which are also useful as protective overcoating layers, and as interface materials for various imaging members. Additionally there is a need for charge transport compounds or copolymers that are nontoxic, and wherein such members are inert to the users thereof. A further need resides in the provision of novel efficient charge transport copolymers which are readily accessible synthetically from inexpensive commercial starting materials.